Okay, so it all started when I got this 1999 Jeep Cherokee 4.0 6 Cylinder and whenever it warmed up to normal temp, if I turned it off it wouldn't start again. Dealt with it for a few months and the most recent issue is as follows.

Started off about a week ago if I applied the throttle too fast or to much from a stop, it would sputter like once and be fine.. VERY rarely would it even do it..

Then, about Tuesday or Wednesday it got to the point that I had to ease into the throttle very very gently to get it to move..

As of today I can start the vehicle, and the vehicle will rev just fine, will idle just fine, I can put it into gear and it will idle just fine, but if I take my foot so much as off the brake it will stall out to like <500 RPM and just sit there until it stalls out completely.

BUT!

If I put the jeep into reverse gear, I can floor it and it's not affected. I can also floor it in park and neutral and it's not affected.

SO FAR : I have replaced the fuel pump, Crank Position Sensor, and put Autolite Platinum spark plugs in... They were the only half way decent spark plugs I could get at 11:00 at night. Fuel pump is an Airtex and the CPS is a Borg Warner.

I have also taken the front O2 sensor completely out and still no avail. And put in a new air filter.

We have tried unhooking the brake booster vacuum line thinking it was getting too much fuel and bogging the motor down on fuel.... Nothing.

Unhooked the IACV sensor, nothing..

I was reading about 35 Psi before the fuel pump was in, and about 50-55 after the install.

I have searched and can't find an existing issue quite like this one.. It seem like everyone out there has found quick easy fixes that I've already tried...

 

Okay. Extremely important question. Are they Walmart plugs?????

Ive bought thres sets from Walmart. One set for the cherokee, one set for my wifes infinity, and one set for my g6 gtp.

Every time the plugs caused crazy misfires. Dying under load, and other wierd spark issues.

If you bought the plugs from Wally world, take them out, and swap them with anything else NOT from Walmart before you do anything else. Sounds crazy im aware, but it has happened on three of three vehicles so far for me

Also that front O2 NEEDS to be hooked up, otherwise you get ****ty misfire, and loss of power.

 

The plugs that came out were Champion RC12LYC and the plugs that went in were Autolite AP985. It was that or Bosch and me and the guy helping me have both had issues with Bosch plugs. They were my only options at Wal-Mart and they were my only option at 11:00PM. Lol. I'm probably going to return them and go back to a Champion plug tomorrow..

Also, the O2 Sensor was plugged in when we were trying all of this.. We tried unplugging it at the very beginning thinking the exhaust would vent through the hole and we could see if it was the cat or not. Haven't tired a new sensor yet.

Also I guess I should mention, the exhaust is broken at the moment right where the muffler is. Just forward of the vehicle of the muffler by like 1/2 an inch.

 

Yeah first things first that 02 sensor NEEDS to be.hooked up. No if and or but's. It will run like garbage without it.

Second, get that Walmart junk out asap. Brand matters, but ive had the exact same model, and brand plugs from Walmart that caused misfires, and from AutoZone that ran good, zero issues.

Dont stress about the exhaust being broken yet, thats not going to causing all this.

after the 02 sensor is back in, flash the computer. Put in plugs not from Wally world. Start her. Give her a sec to re-learn. And let me.know.what happens.

 

1. I work for O'Reilly's so getting good plugs won't be an issue.. I just bought these to see if it was the old *** plugs causing one of my issues.... I will get better ones in tomorrow..

2. How to flash the computer?

3. Should I buy a new O2 Sensor and put that in? If so, I believe the one that we were toying with was the Upstream? I'm not 100%.. My friend was helping A LOT. Lol. Also, at O'Reilly's we only show an Upstream with California emissions. Only show a downstream without.. Issue? I would assume so.

4. I've had a long *** day and I can still smell gas. Lol. I'm off to bed, so I will update tomorrow as the day progresses and we try new things.

 

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I know what you mean about the plugs, every time I bought them from Walmart I was being inpatient, and just hoped they would be ok, and it always bit me in the ***

for now I would just put the 02 back in. it could be bad, but id say test out everything else before we move to that. And yep thats the upstream

Im not 100% since its a 99, but I dont see why it would be different for flashing the computer. Disconnect the battery, and put the positive, and negative cables together for about 5 min. I just zip tie them together while im working on other stuff.

A good night of sleep is very helpful when things get stupid, so smart move. Update when you can and ill try to help as much as I can

 

As of today. I'm getting a late start but with a tool box consisting of screwdrivers (just moved and didn't bring anything) and borrowing tools from O'Reillys I'm going to install a new O2 sensor and flash the computer just as a starting point.

I also have a new TPS, IACV, and MAPS to try one by one.. If none of that fixes it the parts are going back and I'm going to seek professional help... Hopefully.. >_>

Money isn't exactly flowing in and I'm just about at my credit limits.. We will see what happens in the next few hours.

 

You would save money by having a pro check it out first, instead of throwing expensive parts at it. Shotgun diagnostics always cost you more money in the long run.

 

Replaced front O2 sensor. Flashed computer. No change.

Replaced TPS with O2 sensor in tact. No change.

Took TPS off, put old TPS back on, put new IACV on. No change.

Next?

 

A lot of folks have had issues with aftermarket sensors from chain stores, particularly Autozone and O-Reilly's. My replacement sensors always come from Jeep. NAPA is second option if I can't get them from Jeep. Your issue sounds like TPS related.

 

Update :

With Brand New Bosch O2 Sensor and Borg Warner TPS, IACV, and CPS. No change.

With TPS unplugged completely it would last about 2-3 inches of letting off the brake and stall out.

Any other thoughts?

 

Have you swapped plugs yet?

 

Ive had this exact issue. Im not shotgun diagnosing. Im saying what my issue was, and what did fix the issue

 

When you finally do replace the plugs, go with the champion number that is listed under the hood. Autolites don't run worth a damn in Mopar products for some reason. If it calls for standard copper ones, put those in there. I pulled autolite plats out of mine and gained idle quality, power, and mpg.

 

Update :

Left all of the new sensors on. Found a broken ground strap on the back of the motor. Make-shifted a halfway decent ground strap. Tried a few different combinations of some sensors plugged in, other not connected. Nothing.

Out of frustration a friend of mine took a rubber mallet and started beating on the cat. Started it back up and it ran fine even with foot almost off the brake. So we then punched the cat from back to front to try and clear it out.. And thus, it moved. Move forward about 10-15 feet in drive foot completely off the brake. It even handled a very very small amount of throttle to give it a nudge. This was with TPS and IAC unplugged.

However, when my friend went to put the jeep into reverse it stalled and would not start back up. We reconnected the sensors and tried again. No start.

No start. ...

We gave up.. Everyone has to be at work tomorrow and it was late.

I am not going into work tomorrow, and will continue to try and get this thing running..

Any other info will still help. I still am not sure what exactly I'm doing.